Magnetic Fields From Wiring, Appliances and Beds

They are measured with a gaussmeter, in milligauss (mG). A veteran inspector aimed for under 1 mG wherever people sit or sleep for long stretches, and as close to zero as practical. A survey she cited put the typical home at about 0.3 mG. Some scientists she followed drew the line at 1 mG for long exposure; less cautious ones accepted 2 to 2.5 mG.

Evidence: Inspector's practice (precautionary).

An inexpensive meter works for home use, since the numbers that count are at the low end of its scale. With a single-axis meter, turn it slowly in each spot until you find the highest number. Switch on one light on each circuit so current is flowing, and measure again at dinnertime or on a hot summer evening, when household use peaks.

• Wiring errors. A local electrical inspector once told her the average house has several. A faulty neutral connection can raise fields through the whole house, and one bad circuit can behave like a small power line in the living room.
• Current on the water pipes. When a home's electrical return path is poor, current can travel on metal water pipes, sometimes from neighboring houses through the water main. It shows up as a high reading on the first floor above where the water line enters. Correcting it is a job for a licensed electrician, sometimes with a licensed plumber or the utility company.
• The meter and panel. Do not put a bed or favorite chair against the other side of the wall where the service comes in or the panel hangs.
• Motors, transformers and heating coils: hair dryers, purifiers, fans, plug-in clocks, fluorescent ballasts, low-voltage lighting transformers and electric heat. Keep these out of much-used spots and off the ceiling below a bedroom.
• Sources through the wall. Before placing a bed, crib or reading chair, check what is plugged in or running on the other side.
• Power lines. These cannot be fixed later, so measure before you buy or rent.

Distance is the cheapest fix. Step back from running appliances, move the bed, or switch to battery power. Leave any change to wiring or grounding to a licensed electrician.

Innerspring mattresses and metal box springs often pick up permanent, jumbled magnetism during manufacture. To check, set a compass on a clipboard and pull it slowly from one side of the bed to the other. A needle that barely moves is good. One inspector watched the needle spin all the way around at the new bed of a client who had not been sleeping well. If you have been sleeping badly, it is still worth asking your doctor too: if you snore, wake up gasping or still feel unrefreshed after a full night, ask about a sleep study, because sleep apnea is common, treatable and easy to miss. Metal near the bed can also pick up electric fields and radio signals like an antenna. Her preference was a bed with no metal parts, chosen from low-toxic materials rather than ordinary foam.

She was wary of therapeutic magnets, which are strong next to the body's own faint fields and can permanently magnetize innersprings. She reported that one night on a magnetic mattress pad left her with brain fog that lasted months.

Evidence: Inspector's practice (precautionary).

Current guidance: The NIH center for complementary health finds no good evidence that static magnets treat pain, and considers them generally safe except near pacemakers and similar devices.

Current guidance: IARC classes extremely low frequency magnetic fields as possibly carcinogenic (Group 2B, 2002), based mainly on a weak but repeated link between childhood leukemia and average home fields above about 3 to 4 mG. WHO says a cause has not been shown, and international exposure limits sit far above her 1 mG target. Her target is a precaution, not an official standard.

This page is for education only. It is not medical, legal or engineering advice. The inspector whose work this builds on was an environmental consultant, not a physician. Talk with your doctor about health concerns, and use licensed professionals for electrical work and large mold jobs. Products, prices and labs mentioned reflect the years they were recorded and may have changed.

Source: the field work of environmental inspector May Dooley, MS, MA, CMC

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